Method of making sulphur trioxide



2 range at which vanadium acts as. a; catalyst} in Patented Dec. '26,

f am

t METHOD on MAKmG smimwngmmoxlmzl l A1iin ngneares ey, Plainfield, N. i.J.,

" Napoleon Arthur L'aury;

a tRock ll ante 1 N; Y; fassi'gn ors to The' camp Chemical Company,:Inc.,- Boiind 'Bi-ookfiNr-,Lfa corporation g I Ne [Dr lwi g.AimlicationMay. 13, 19,29.

' iifleia msq (01.: 23-475) '7 been recognized, and vanadium has tosomeex tentlbeen used as a catalyst inicarrying out'the"methodcommercally. h we havediscovered that the catalytic, action ofvanadium in causing a reaction betweenlsulphur dioxide gas and oxygen isgreatly'gin'cre'ased by the presence ofitherareelement caesium, and thatcesium acts asa promoter to .the'fcatalytic action of vanadium, andserves both tov increase the catalytic. act? on throughout, thetemperature this reaction and to extend thisteniperature range downwardto a material extend Our invention, which is based on this idisco v-'fery, consists in improving the contact methodf 5v of mak ng sulphuricacid by using a vanadium catalyst with caesium as a promoter and mavanadiumand caesium catalyst for use in said method.

While catalytic masses embodying the inven- ,tion may be made innumerousdiiierent Ways. we will, for the sake of illustration, describea specific method for making such a mass which we have foundsatisfactory and effective in practice:

An aqueous solution of ammonium meta-vanadate (NHiVOg) is prepared. Inthis solution is immersed a porous carrier, such as Celite (tradenameapplied to diatomite or diatomaceous earth sold by the'Johns ManvilleCorp., of 292 Madison Ave, N. Y. C.) chips calcined at about l000 C.When the carrier has absorbed the solutionto saturation, it is removedand dried at 110C. It

is then again immersed in the solution and dried,

and the process is repeated till all the solution has been absorbed inthe carrier. An aqueous solution of caesium chloride (CsCl) is thenapplied to the carrier by sprinkling. After satura-' tion with caesiumchloride, the carrier is dried atv 110 C.

We have found that the action of caesium asa promoter to the catalyticaction of vanadium shows material increase with an increase in theproportion of caesium present up to the point at which the amount ofcaesium in the mass is,

atomically, three times that of the vanadium.

gaaLiThe proportion of the caesium may be varied within this limit tosatisfy conditions of use in which the maximum promotion is unnecessary.Adesirable composition for commercal-purposes is one in which theamounts of vanadium. and

caesiumareapproximately atomically equal. To 1:

prepare such a, mass" by the above method the proportions ofthesoluble-salts and the carrier usedare as follows: r V

Ammonium meta-vanadate l lpart by weight Caesium chloride 1.44 parts'byweight 653 Carrier (calcined Celite)' 6.3 pa'rts by weight is desirablefthough not essential, to heat thefimpregna'ted.carrier .upto about 500C. in

an atmosphere containing SOzb'efore using the 763. mass o "Inlthemanufactureof sulphuric acid in accord ahce with .our invention, a.mixture containing oxygen ;and sulphur dioxide gases is passed throughaconverter charged, with the contact mass" above described. Theheatevolved by, the combination ofthe gases coming in c ontact withthefjfcatalyst {is systematically removed during the passage ofjthe'gasesf through the converter,

so that the temperature oithe gas in contact with thecatalystisreducedto' a temperature of about 420 C. as it leaves *the"catalyst, material conversion taking place at thelower temperature,

and affording a total conversion of 98%.

Comparative tests of the catalytic mass above 5::

described and a vanadium contact mass precisely similar in all respectswith the mass described,

except for the omission of the caesium, show that at all temperatures,from 375 C.'to 500 C., the

percentage of conversion of S02 and 0 into S03 is materially-increasedby the presence of the caesium, and that particularly at temperaturesbelow 450 C. at which little conversion is obtained by the masscontaining vanadium only, very material conversion is obtained by themass con- 05' taining vanadium and caesium.

Our invention is by no means limited to a catalytic mass prepared inaccordance with the specific methodwhich has been given as anillustration. This method may readily be modified 100 by thesubstitution of chemical equivalents,

such as the use of other soluble vanadium compounds, instead of theammonium meta-vanadate. Furthermore, although we have found that anadvantage is gained by caesium as a chloride or other neutral salt of amineral acid, it is nevertheless true that, satisfac tory conversion maybe obtained if other soluble caesium compounds are substituted for suchsalts.

Furthermore, it is not essential to apply the 1 0 introducing thevanadium solution and the caesium solution to the carrier separately.The solutions may be mixed before application to the carrier, or asingle solution of a single soluble salt, such as caesium-vanadate(CSVOs) may be used with good results. The references to solutionscontaining vanadium and caesium in the claims which follow should,therefore, be understood to include a single solution of a single salt,except where separate solutions are expressly specified.

What is claimed is: a e

l. A catalyst for use in the contact method of making sulphuric acid,comprising vanadium and caesium, in which the gram-atoms of caesium areless than four times the gram-atoms of vanadium.

2. A catalyst for use in the contact method of making sulphuric acid,comprising vanadium,

and caesium, in which the gram-atoms of caesium are approximately equalto the gram-atoms of vanadium.

3. A catalytic mass for use in the contact method of making sulphuricacid, comprising a porous carrier, and Vanadium and caesium on a thesurface and in the pores of said carrier.

4. A catalytic mass for use in the contact method of making sulphuricacid, comprising porous particles of substantially pure silica, andvanadium and casium on the surface and in the pores of said particles.

5.A catalytic mass] for use in the contact method of making sulphuricacid, comprising a porous carrier of the type of calcined diatomite,which has been impregnated with soluble salts containing vanadium andcaesium. 6. A catalytic mass for use in the contact method of makingsulphuric acid, comprising a porous carrier of calcined diatomite, whichhas been impregnated with a soluble salt containing vanadium and aseparate soluble salt containing caesium.

7. A catalytic mass, for use in the contact method of making sulphuricacid, comprising a porous carrier, which has been impregnated withsolutions containing vanadium and caesium, and which has been heatedafter impregnation, and

previous to use, in an atmosphere containing sulphur dioxide.

8. A catalytic mass for use in the contact method of making sulphuricacid, comprising a porous carrier of calcined diatomite, which has beenimpregnated with a vanadate solution and a separate solution containingcaesium, and which has been heated after impregnation, and previous touse, in an atmosphere containing sulphur dioxide. I

9. A catalytic mass for use in the contact method of making sulphuricacid, comprising a silica carrierwhich-has been impregnated withavanadium solution and a solution of a neutral caesium salt of a mineralacid.

10. A catalytic mass for use in the contact methodof making sulphuricacid, comprising a silica carrier which has been impregnated with avanadium solution and a solution of caesium chloride.

11. The method of making sulphur trioxide, which consists in passing amixture of gases containing oxygen and sulphur dioxide atan elevatedtemperature through a catalytic mass which consists of porous particlesof substantially pure silica impregnated with solutionscontaining'vanadium and caesium, H

' 12. The method of making sulphur trioxide, which consists in passing amixture of gases containing oxygen and sulphur dioxide at an elevatedtemperature through a catalytic mass consisting of a porous carriercarrying vanadium and caesium, and in reducing the temperature of thegases so that as they leave the mass they are at approximately 420 C.

13, A catalyst for use in the contact method of making sulphuric acidcomprising vanadium and caesium in non-zeolitic relation with respect toeach other, the catalyst being deposited upon an inert carrier. 7

14. A catalyst for use in the contact method of making sulphuric acidcomprising a siliceous carrier having Vanadium and caesium deposited innon-zeolitic relation upon the surface thereof.

' ALLING P. BEARDSLEY.

NAPOLEON ARTHUR LAURY.

